1. Field of the Invention
Embodiments disclosed herein relate generally to methods of completing a well with a sand screen. In particular, embodiments disclosed herein relate generally to wellbore fluids used in completing a well with a sand screen.
2. Background Art
During the drilling of a wellbore, various fluids are typically used in the well for a variety of functions. The fluids may be circulated through a drill pipe and drill bit into the wellbore, and then may subsequently flow upward through wellbore to the surface. Common uses for well fluids include: lubrication and cooling of drill bit cutting surfaces while drilling generally or drilling-in (i.e., drilling in a targeted petroliferous formation), transportation of “cuttings” (pieces of formation dislodged by the cutting action of the teeth on a drill bit) to the surface, controlling formation fluid pressure to prevent blowouts, maintaining well stability, suspending solids in the well, minimizing fluid loss into and stabilizing the format ion through which the well is being drilled, fracturing the formation in the vicinity of the well, displacing the fluid within the well with another fluid, cleaning the well, testing the well, transmitting hydraulic horsepower to the drill bit, fluid used for emplacing a packer, abandoning the well or preparing the well for abandonment, and otherwise treating the well or the formation.
Once the well has been drilled and a hydrocarbon reservoir has been encountered, the well is ready to be completed. In the course of completing a well, it is common practice to run a string of casing into the well bore and then to run the production tubing inside the casing. At the producing interval(s) of the formation, perforations are typically created to extend through the casing string, through the cement that secures the casing string in place, and a short distance into the formation. These perforations may be created by detonating shaped charges carried in a perforating gun. The perforations created cross one or more production zones to allow production fluids to enter the interior of the wellbore.
Once the perforations are created, however, the formation pressure must be controlled. Typically, this is achieved by loading a completion fluid into the wellbore during the completion process. The completion fluid is selected to have a density sufficient to create an overbalanced hydrostatic pressure regime at the location(s) of the wellbore perforations, thereby preventing formation fluids from entering the wellbore.
After the well is perforated, a stimulation or sand control treatment process may be performed. Sand control processes may prevent, after the well is completed and placed in production, formation sand from unconsolidated formations being swept into the flow path along with formation fluid, which erodes production components in the flow path. Similarly, in uncased boreholes, where an open face is established across the oil or gas bearing zone, formation sand from unconsolidated formations may also be swept into the flow path along with formation fluid.
Thus, with either cased or uncased well bores, one or more sand screens may be installed in the flow path between the production tubing and the perforated casing.
Additionally, the annulus around the screen may be packed with a relatively coarse sand or gravel which acts as a filter to reduce the amount of fine formation sand reaching the screen and seals off the annulus in the producing zone from non-producing formations. When the sand tries to move through the gravel, it is filtered and held by the gravel and/or screen, but formation fluids continue to flow unhindered (by either the gravel or screen) into the wellbore.
Following the treatment process, it is typically necessary to have the completion fluid remain in the wellbore to control formation pressure during the remainder of the completion process. Typically, these processes includes tripping portions of the work string out of the wellbore and installing a production tubing string within the wellbore to provide the conduit through which formation fluids travel from the formation depth to the surface. In addition, the production tubing string may include various operating tools including flow control devices, safety devices and the like which regulate and control the production of fluid from the wellbore. Once the production tubing string has been installed and the completion fluid is removed from the well, production may begin.
Conventionally, the fluid used during drilling operations contains solid weighting agents, viscosifying solids, and other solids in order to produce a fluid having the density and Theological properties required for drilling the well. However, if the solids-laden fluid is still in the wellbore during the completion operation and placement of equipment, the solids present in the fluid can potentially plug the screens and severely impair production rates. Thus, a completion fluid is typically used to displace the drilling fluid and to run the sand-exclusion equipment and gravel packing tools in a generally solids-free environment.
High-density completion fluids are often necessary in well completions to maintain sufficient hydrostatic pressure to control the bottom hole pressures of the producing zones for relatively higher pressure producing zones. However, high-density completion brines can be very expensive, dangerous to field personnel, and often times damaging to the producing zones.
Accordingly, there exists a continuing need for wellbore fluids that can be used in completion operations.